Can ordinary hi-fi speakers reproduce guitar speaker sounds (the "scratching paper" sound) ? Can they reproduce any waveform the microphone has captured?

If yes then surely we could make an electronic circuit to go inside guitar amps and allow them to use ordinary, mass produced, cheap PA speakers rather than expensive, low volume, specially made guitar speakers?

That's not the reason some guitar cabs are even extremely expensive. Guitar cabs are not speakers in the strictest sense of the word, they're instruments. The same guitar sounds very different on different speakers and with different effects. The sound of a guitar is combination of all these things and not the just the guitar itself.

You can get extremely cheap guitar cabs too because basically they're just a pair (or 2 pairs) of full-range drivers with high-Q, high sensitivity and a frequency linearity as jagged as the Badlands, combined with an underpowered amplifier.

You can get extremely cheap guitar cabs too because basically they're just a pair (or 2 pairs) of full-range drivers with high-Q, high sensitivity and a frequency linearity as jagged as the Badlands, combined with an underpowered amplifier.